810 HEWITT AND ASTON:

LXXII1.-Bromination of Benzeneaaophenol. Part 11. By JOHN THEODORE HEWITT and WILLIAM GEORGE ASTON.

IT has been recently shown by the authors that when benzeneazo- phenol is brominated in a glacial acetic acid solution containing excess of fused sodium acetate, two bromine atoms enter the phenol nucleus in the ortho-position relatively to the hydroxyl group (Trans., 1900, 77, 712). I n the absence of sodium acetate, a bromo-derivative of unknown constitution was obtained, the investigation of which forms the subject of the present communication.

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BROMINATION OF BENZENEAZOPHENOL, FART 11. 811

p- Bromo ben~eneccxodibromo~henol.

When benzeneazophenol is dissolved in five times its weight of glacial acetic acid and treated with one molecular proportion of bromine, only a portion of the azophenol is attacked, for on pouring into water, collecting the precipitate, and recrystallising i t a few times from glacial acetic acid, a compound is isolated which is sparingly soluble in cold acetic acid and melts at 143-145' (uncorr.). The various prep- arations were found to contain a percentage of bromine corresponding with that required for the forniula C,,H70N2Br,.

Experiments were then made on the bromination of benzeneazo- phenol suspended in water, molecular proportions being again employed, but the same brominated product was obtained, although, owing t o the reaction not having proceeded so smoothly as in acetic acid solu- tion, the melting point was generally a degree or two lower.

Finally, it was found that a satisfactory yield of the substance might be obtained by the following procedure. Ten grams of finely powdered benzeneazopbenol are suspended in 50 grams of glacial acetic acid, the mixture being well cooled by ice, and stirred while 25 grams of bromine diluted with 25 grams of glacial acetic acid are gradually added. The bromine is used up rapidly, and only a trace of it can be detected a t the end of the operation if the above quantities are em- ployed. The product is poured into water, the precipitate collected, washed, and recrystallised from glacial acetic acid. The brownish- orange needles so obtained were analysed with the following result :

0.1743 gave 0.2125 CO, and 0.0331 H20. 0.1924 ,, 0.2489 AgBr. Br = 55-04. 0.2603 ,, 15-6 C.C. moist nitrogen a t 18' and 766 mm. N = 7.27.

C,,H70N,Br,requiresC=33~10; H= 1.63; Br=55*14;N=6*45percent.

The substance melts a t 148' (cow.), and dissolves in acetone, ethyl alcohol, ethyl acetate, benzene or its homologues, aniline or nitro- benzene ; it is less soluble in cold glacial acetic acid, and dissolves very sparingly in light petroleum, On treatment with concentrated sulphuric acid, the substance yields a dark red sulphate of the corresponding quinonehydrazone, the azophenol separating as a yellow precipitate on the addition of water.

Conclusive evidence in favour of the view that the substance is p-bromobenzeneazodibromophenol was obtained by brominating p-bromobenzeneazophenol in presence of sodium acetate, and benzene- azo-o-dibromophenol in presence of strong sulphuric acid. The same substance was obtained in both cases, and proved to be identical with the product obtained by the direct action of bromine on benzene-

C = 33.25 ; H = 2.11.

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81 2 HEWITT AND ASTON:

azophenol ; each preparation causing no depression of the melting point of the others.

Bromincction of Benzemaxodibrontopheno1.-Twenty-four grams of benzeneazodibromophenol were suspended in 290 grams of glacial acetic acid mixed with 24 grams of concentrated sulphuric acid, and to the well cooled mixture, 11 grams of bromine, diluted with 44 grams of glacial acetic acid, were slowly added. The product was recrystal- lised from acet,one, and melted at 148'.

Bromination of p-Bromobenxeneaaophenol,-~ .3 grams of p-bromo- benzeneazophenol were dissolved in 50 grams of acetic acid together with 1.3 grarrs of fused sodium acetate. The solution was well cooled, and 1.5 grams of bromine in 4 grams of acetic acid added. The pro- duct, after recrystallisation, melted at 148'.

The production of p-bromobenzeneazo-o-dibromophenol can be shown diagrammatically as follows :

\- /-)N2/-\OH \d' Br

In aqueous suspension or - Bri/-\N,/-\OH acetic acid SOlUtiOD. / \-/

Br In acetic acid solution in /

111 acetic acid I solution in presence of sodium acetate.

Br/-\N,/-\OH

I

\ / \-/

presence of sodium acetate.

Br 1

/-\N,/-\OH \--/ \-/ Br

The acetyl derivative was obtained by boiling p-bromobenzeneazo- dibromophenol for 1 hour with an equal weight of fused sodium acetate and three times its weight of acetic anhydride. It separates from glacial acetic acid in very small crystals, but in larger, orange prisms from chloroform in which it is easily soluble. The melting point is 167'.

0.1460 gave 0.1883 CO, and 0.0359 H,O. C135.17; H = 1.97. Cl,H,02N2Br, requires C = 35.22 ; H = 1-89 per cent.

The compound is very soluble in carbon disulphide and moderately so in aniline, benzene, toluene, nitrobenzene, ethyl ether, ethyl acetate, or ethyl benzoate, but dissolves only sparingly in cold acetone, amyl or ethyl alcohol, or light petroleum.

The bernxoyl derivative was prepared by boiling the azophenol for 1 hour with 24 times its weight of benzoyl chloride, and was recrystal- lised from a large excess of spirit, in which, even at the boiling point, it is but very sparingly soluble. It forms brownish-orange needles melting at 129'.

IYr6.00. 0.2188 gave 13.4 C.C. moist nitrogen a t 16' and 750 mm. C1,H,,O2N2Br, requires N = 5-21 per cent,

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BROMINATION OF BENZENEAZOPHEKOL. PART 11. 81 3

The substance is taken up sparingly by acetic acid, ethyl alcohol, or petroleum spirit; it is fairly easily soluble in carbon disulphide, benzene or its homologues, or aniline, whilst in the remaining organic solvents its solubility is moderate.

The ethyl ester was obtained by heating 5 grams of the azophenol with 0.7 gram of caustic potash, 1.6 grams of ethyl bromide, and about 50 C.C. of absolute alcohol in a sealed tube for 1+ hours a t 105-110'. After cooling, the contents of the tube were warmed on the water-bath with dilute caustic soda, the insoluble ethyl ether collected, washed, dried, and recrystallised from benzene. Beautiful, golden needles melting at 125' were obtained, which were very soluble in carbon disulphide and dissolved fairly easily in ether, ethyl benzoate, or hydrocarbon solvents, The solubility in acetone, ethyl alcohol, or amyl alcohol was slight.

0.1027 gave 0.1361 CO, and 0.0203 H20. C1,Hl,ON,Br, requires C = 36.28 ; H = 2.40 per cent.

TribromobenxeneccxophenoL--As it seemed a t one time possible that the substance obtained by the direct action of bromine on benzeneazo- phenol might be tribromobenzeneazophenol, the latter was synthetically prepared by coupling diazotised tribromoaniline with phenol. The only azo-compound derived from tribromoaniline, so far as the authors know, is the tribromobenzeneazodimethylaniline described by Sil hers tein (J. pr. Chm., 1883, [ ii], 27, 113). Since Silberstein's method of diazotising tribromoaniline is rather tedious, the process we adopted may be described, as it is simple. 13.2 grams of finely powdered tribromoaniline were dissolved in 15 C.C. of concentrated sulphuric acid, a finely divided precipitate of the base or its sulphate being obtained by the addition of 5 C.C. of water. The well-cooled mixture was diaaotised by adding 2% grams of .pure, solid sodium nitrite in small portions at a time, left for 2 hours, and then poured on t o crushed ice. Ten minutes later, the solution was added to 4 grams of phenol and 40 grams of sodium carbonate, (Na,CO,,H,O), dissolved in 300 C.C. of water and cooled to - lo. The precipitated azo-compound was collected, washed, and extracted with hot dilute caustic potash solution, the filtrate precipitated by hydrochloric acid and the azophenol recrystal- lised from glacial acetic acid. Small, bright, orange prisms mere obtained melting at 168.5'.

C = 36.14 ; H = 2.20.

0.2627 gave 0.3229 CO, and 0.0382 H20. C = 33.41 ; H = 1.68. CI2H70N2Br, requires C = 33.10 ; H = 1-63 per cent.

Tribromobenzeneazophenol is easily soluble in acetone or et hy 1 acetate, dissolves fairly well in ethyl alcohol, ethyl ether, acetic acid, or benzene, but is only very sparinglysoluble in light petroleum. For

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814 MORGAN: ACTION OF FORMALDEHYDE ON

further characterisation, the acetyl and benzoyl derivatives were prepared.

Acetyl Derivative.-The acetylation was carried out with fused sodium acetate and acetic anhydride, and the substance recrystallised from glacial acetic acid, Thus o6tained, it forms small, red, radiating groups melting at 105'.

N = 6-54, 0.2462 gave 1 3 5 C.C. moist nitrogen at 12' and 762 mm. C1,H90,N2Br, requires N = 5.89 per cent.

The benzoyl derivative was obtained by the Schotten-Baumann method and recrystallised from boiling amyl alcohol in which it is not very soluble.

N = 5.41. 0.2704 gave 12.3 C.C. moist nitrogen at 12' and 762 mm.

It is an orange-pink, crystalline powder which, as seen under the It

Cl,HllBr,02N2 requires N = 5.21 per cent.

microscope, consists of radiating groups of very small prisms. melts a t 132' and is very sparingly soluble in the usual solvents,

EAST LONDON TECHNICAL COLLEGE.

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